Long Mott Energy, LLC – Long Mott Generating Station Xe-100 Power Reactor Application
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Project Overview
The staff of the U.S. Nuclear Regulatory Commission (NRC) is currently engaged in review activities for the construction permit application from Long Mott Energy, LLC (LME), for the Xe-100 power reactor to be located in Calhoun County, Texas. The Xe-100 project is supported by the U.S. Department of Energy’s Advanced Reactor Demonstration program and would be used to demonstrate the X Energy Xe-100 reactor technology.
| Plant Characteristics |
Description |
| Reactor Type |
High-Temperature Gas-Cooled Reactor (HTGR) |
| Containment Type |
Functional Containment: Uranium Oxy carbide (UCO) fuel kernel, TRIstructural ISOtropic (TRISO) particle fuel layers, Fuel matrix, Helium pressure boundary, (see SECY-18-0096 for a description of functional containment) |
| Power Level |
4-Module plant with 800 MWth/320 MWe |
| Fuel |
Graphite Pebbles with TRISO Particle fuel |
| Balance of Plant |
Shared steam powered conversion system (Rankine Cycle) |
Key Milestones
| Milestones |
Completion Date
Actual - A
Target - T |
| Application Tendered |
03/31/2025 |
| Acceptance Review |
| Acceptance Review Start |
04/01/2025 – A |
Docketing Decision Letter
Issued/Acceptance Review Complete |
05/12/2025 – A |
| Review Schedule Established/Schedule Letter Issued to Applicant |
06/10/2025 – A |
| Safety Review |
| Draft Safety Evaluation — Safety Evaluation (SE) sections drafted, and information gaps identified. |
February 2026 – T |
| *Advanced Safety Evaluation — All SE sections available for Advisory Committee on Reactor Safeguards review. |
August 2026 – T |
| Final Safety Evaluation — Final SE issued. |
November 2026 – T |
| Environmental Review |
| **Develop Initial Environmental Assessment (EA) Inputs — Draft EA sections and appendices developed, open items identified, audit plan and information needs issued, and site audit conducted. |
September 2025 – T |
| Revise Environmental Assessment — Initial EA sections updated; site audit completed, and information needs resolved. Applicant submittals completed. Appendices completed and EA prepared. |
October 2025 – T |
| Finalize Environmental Assessment and Related Activities — Legal review and management approvals of EA/FONSI conducted; EA correspondence prepared. |
February 2026 – T |
| Issue Environmental Assessment and Finding of No Significant Impact — EA/FONSI concurrence completed; publication and issuance activities completed (including all related correspondence). |
June 2026 – T |
| Hearing |
TBD |
| Construction Permit Decision |
TBD |
* The review team will begin interacting with the Advisory Committee on Reactor Safeguards (ACRS) as soon as portions of the safety evaluation are approved by NRC staff managers. The ACRS may write a letter to the staff commenting on the evaluation.
** The NRC staff has made a decision to first prepare an Environmental Assessment to document its review of the environmental impacts associated with the proposed Long Mott Generating Station. In accordance with the National Environmental Policy Act, at the conclusion of this process, a determination will be made regarding whether to prepare a Finding of No Significant Impact (FONSI) or an Environmental Impact Statement (EIS). If a FONSI cannot be reached the NRC will commence preparing an EIS and this schedule may be subject to change.
| Contacts for Long Mott Generating Station Xe-100 Power Reactor |
| Safety Project Manager |
Adrian Muñiz
301-415-4093 |
| Environmental Project Manager |
Joe O’Hara
301-415-6854 |
| Public Affairs Officer |
Scott Burnell
301-415-8204 |